New Fourier transform infrared based computational method for peptide secondary structure determination. II. Application to study of peptide fragments reproducing processing site of ocytocin-neurophysin precursor

A new method for the quantitative determination of the percentage of intram olecular H-bonds, based on Fourier transform infrared techniques, is applie d to the conformational analysis of a series of synthetic peptides spanning the processing site of the ocytocin and neurophysin precursor. Even though the method uses traditional tools such as Fourier self-deconvolution, the Nth derivative, and curve-fitting procedures for the analysis of the spectr a, the assignment of the absorptions due to peptide groups participating in to secondary structures is based on the direct observation and quantificati on of the isotopic effect induced on the groups participating in intramolec ular H-bonds in the presence of organic solvents. This permits the quantifi cation of the different populations of molecules containing intramolecular H-bonds involved in p-turns and cu-helices. The results are consistent with those previously obtained by NMR techniques in the same solvent systems. ( C) 2001 John Wiley & Sons, Inc.